Understanding Quaternion to DCM Conversion in Openshoe Matlab Library

[namster]

Summary:: Conversion from quaternion to DCM

Hi All ,
our teacher asked us to try to understand the openshoe Matlab library , i stagnate on function that convert the quaternion to DCM i have found many example on website but the description of matrix are diffrente that the one is used on openshoe but it give the same result , so i wan't to know which of this matrix is correcte ?

 

[jedishrfu]

Are you using this library?

https://sourceforge.net/p/openshoe/home/Home/

or some other one?

 

[namster]

Are you using this library?

https://sourceforge.net/p/openshoe/home/Home/

or some other one?

yes that's it , i use the Matlab implementation http://www.openshoe.org/?page_id=362

function R=q2dcm(q)

p=zeros(6,1);

p(1:4)=q.^2;

p(5)=p(2)+p(3);

if p(1)+p(4)+p(5)~=0
   p(6)=2/(p(1)+p(4)+p(5));
else
   p(6)=0;
end
%[ 1-p(6)*p(5) p(6)-p(5)           p(6)+p(5)
%  p(6)+p(5)   1-p(6)*(p(1)+p(3))  p(6)-p(5)
%  p(6)-p(5)   p(6)+p(5)           1-p(6)*(p(1)+p(2)) ]

R(1,1)=1-p(6)*p(5);
R(2,2)=1-p(6)*(p(1)+p(3));
R(3,3)=1-p(6)*(p(1)+p(2));

p(1)=p(6)*q(1);
p(2)=p(6)*q(2);
p(5)=p(6)*q(3)*q(4);
p(6)=p(1)*q(2);

R(1,2)=p(6)-p(5);
R(2,1)=p(6)+p(5);
p(5)=p(2)*q(4);
p(6)=p(1)*q(3);

R(1,3)=p(6)+p(5);
R(3,1)=p(6)-p(5);

p(5)=p(1)*q(4);
p(6)=p(2)*q(3);

R(2,3)=p(6)-p(5);
R(3,2)=p(6)+p(5);

end